diff --git a/futures-channel/src/mpsc/mod.rs b/futures-channel/src/mpsc/mod.rs index 854ba34935..e8cd8ba0f0 100644 --- a/futures-channel/src/mpsc/mod.rs +++ b/futures-channel/src/mpsc/mod.rs @@ -1020,9 +1020,6 @@ impl Receiver { /// It is not recommended to call this function from inside of a future, /// only when you've otherwise arranged to be notified when the channel is /// no longer empty. - /// - /// This function will panic if called after `try_next` or `poll_next` has - /// returned `None`. pub fn try_next(&mut self) -> Result, TryRecvError> { match self.next_message() { Poll::Ready(msg) => { @@ -1186,7 +1183,10 @@ impl UnboundedReceiver { } fn next_message(&mut self) -> Poll> { - let inner = self.inner.as_mut().expect("Receiver::next_message called after `None`"); + let inner = match self.inner.as_mut() { + None => return Poll::Ready(None), + Some(inner) => inner, + }; // Pop off a message match unsafe { inner.message_queue.pop_spin() } { Some(msg) => { diff --git a/futures-channel/tests/mpsc-close.rs b/futures-channel/tests/mpsc-close.rs index 9eb5296d88..3d6bd0a71c 100644 --- a/futures-channel/tests/mpsc-close.rs +++ b/futures-channel/tests/mpsc-close.rs @@ -276,3 +276,14 @@ fn stress_try_send_as_receiver_closes() { bg.join() .expect("background thread join"); } + +#[test] +fn try_next_after_none() { + let (tx, mut rx) = mpsc::unbounded::(); + // Drop the sender, close the channel. + drop(tx); + // Receive the end of channel. + assert_eq!(Ok(None), rx.try_next().map_err(|_| ())); + // None received, check we can call `try_next` again. + assert_eq!(Ok(None), rx.try_next().map_err(|_| ())); +}